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+UNICHARSET(5)
+=============
+:doctype: manpage
+
+NAME
+----
+unicharset - character properties file used by tesseract(1)
+
+DESCRIPTION
+-----------
+Tesseract's unicharset file contains information on each symbol
+(unichar) the Tesseract OCR engine is trained to recognize.
+
+A unicharset file (i.e. 'eng.unicharset') is distributed as part of a
+Tesseract language pack (i.e. 'eng.traineddata').  For information on
+extracting the unicharset file, see combine_tessdata(1).
+
+The first line of a unicharset file contains the number of unichars in
+the file.  After this line, each subsequent line provides information for
+a single unichar.  The first such line contains a placeholder reserved for
+the space character.  Each unichar is referred to within Tesseract by its
+Unichar ID, which is the line number (minus 1) within the unicharset file.
+Therefore, space gets unichar 0.
+
+Each unichar line in the unicharset file (v2+) may have four space-separated fields:
+
+  'character' 'properties' 'script' 'id'
+
+Starting with Tesseract v3.02, more information may be given for each unichar:
+
+  'character' 'properties' 'glyph_metrics' 'script' 'other_case' 'direction' 'mirror' 'normed_form'
+
+Entries:
+
+'character':: The UTF-8 encoded string to be produced for this unichar.
+'properties':: An integer mask of character properties, one per bit.
+    From least to most significant bit, these are: isalpha, islower, isupper,
+    isdigit, ispunctuation.
+'glyph_metrics':: Ten comma-separated integers representing various standards
+    for where this glyph is to be found within a baseline-normalized coordinate
+    system where 128 is normalized to x-height.
+  * min_bottom, max_bottom: the ranges where the bottom of the character can
+    be found.
+  * min_top, max_top: the ranges where the top of the character may be found.
+  * min_width, max_width: horizontal width of the character.
+  * min_bearing, max_bearing: how far from the usual start position does the
+    leftmost part of the character begin.
+  * min_advance, max_advance: how far from the printer's cell left do we
+    advance to begin the next character.
+'script':: Name of the script (Latin, Common, Greek, Cyrillic, Han, null).
+'other_case':: The Unichar ID of the other case version of this character
+    (upper or lower).
+'direction':: The Unicode BiDi direction of this character, as defined by
+    ICU's enum UCharDirection. (0 = Left to Right, 1 = Right to Left,
+    2 = European Number...)
+'mirror':: The Unichar ID of the BiDirectional mirror of this character.
+    For example the mirror of open paren is close paren, but Latin Capital C
+    has no mirror, so it remains a Latin Capital C.
+'normed_form':: The UTF-8 representation of a "normalized form" of this unichar
+    for the purpose of blaming a module for errors given ground truth text.
+    For instance, a left or right single quote may normalize to an ASCII quote.
+
+
+EXAMPLE (v2)
+------------
+..............
+; 10 Common 46
+b 3 Latin 59
+W 5 Latin 40
+7 8 Common 66
+= 0 Common 93
+..............
+
+";" is a punctuation character. Its properties are thus represented by the
+binary number 10000 (10 in hexadecimal).
+
+"b" is an alphabetic character and a lower case character. Its properties are
+thus represented by the binary number 00011 (3 in hexadecimal).
+
+"W" is an alphabetic character and an upper case character. Its properties are
+thus represented by the binary number 00101 (5 in hexadecimal).
+
+"7" is just a digit. Its properties are thus represented by the binary number
+01000 (8 in hexadecimal).
+
+"=" is not punctuation nor a digit nor an alphabetic character. Its properties
+are thus represented by the binary number 00000 (0 in hexadecimal).
+
+Japanese or Chinese alphabetic character properties are represented by the
+binary number 00001 (1 in hexadecimal): they are alphabetic, but neither
+upper nor lower case.
+
+EXAMPLE (v3.02)
+---------------
+..................................................................
+110
+NULL 0 NULL 0
+N 5 59,68,216,255,87,236,0,27,104,227 Latin 11 0 1 N
+Y 5 59,68,216,255,91,205,0,47,91,223 Latin 33 0 2 Y
+1 8 59,69,203,255,45,128,0,66,74,173 Common 3 2 3 1
+9 8 18,66,203,255,89,156,0,39,104,173 Common 4 2 4 9
+a 3 58,65,186,198,85,164,0,26,97,185 Latin 56 0 5 a
+. . .
+..................................................................
+
+CAVEATS
+-------
+Although the unicharset reader maintains the ability to read unicharsets
+of older formats and will assign default values to missing fields,
+the accuracy will be degraded.
+
+Further, most other data files are indexed by the unicharset file,
+so changing it without re-generating the others is likely to have dire
+consequences.
+
+HISTORY
+-------
+The unicharset format first appeared with Tesseract 2.00, which was the
+first version to support languages other than English. The unicharset file
+contained only the first two fields, and the "ispunctuation" property was
+absent (punctuation was regarded as "0", as "=" is in the above example.
+
+SEE ALSO
+--------
+tesseract(1), combine_tessdata(1), unicharset_extractor(1)
+
+<https://tesseract-ocr.github.io/tessdoc/Training-Tesseract.html>
+
+
+AUTHOR
+------
+The Tesseract OCR engine was written by Ray Smith and his research groups
+at Hewlett Packard (1985-1995) and Google (2006-2018).